The invention is directed generally to a method and apparatus for constructing figures on a display device and, more particularly, to a method and apparatus for constructing figures, such as lines, arcs, and curves using chained three dimensional unit vectors for drawing characters, symbols, and wireframe objects on a display device such as a CRT screen.
Display devices are used to convey information for many applications. In one application, advanced cockpit concepts use helmet mounted display devices to convey information to aircraft pilots. The information presented on such a display must be stabilized due to variations in the helmet and aircraft pitch, roll, and yaw motions. A large computational overhead is associated with the three dimensional nature of the required stabilization. Currently standard rotation algorithms in computer software are used to provide such stabilization. In addition to the stabilization requirements, human factor studies have shown that helmet mounted displays require a higher update rate than conventional head-down display and head-up display devices. Consequently, more computationally intensive information must be displayed in a shorter amount of time than is presently feasible using current devices.
Current display processors construct display formats with two dimensional vectors using a Cartesian coordinate data base. These vectors can use various rotation computer algorithms in computer software to stabilize the image. Unfortunately, the algorithms implemented in software are too slow to meet system requirements for applications such as helmet mounted displays. Co-processors have been used to increase the computational efficiency of processors using such software. However, the use of co-processors does not significantly improve the time consuming rotation algorithms currently used to calculate each x,y point on a Cartesian grid. More computationally efficient data signal processors and data signal processor modules have successfully closed the gap on the time required to compute the x,y points, but have not provided the high update rates required for cockpit display applications.
The invention provides a solution to the above-described computational problem because it does not require the processor to use a rotation algorithm to calculate each x, point. The invention allows the processor to work at a higher level of abstraction without incurring time delays by handling the computational aspects of generating a display. This higher level of abstraction is gained by using polar vectors as building blocks to create straight lines, circular arcs, and arbitrary curves (such as Bezier curves). The abstraction is achieved by virtue of the method in which the three dimensional rotation equations are utilized by the invention. The method uses a unit vector along the x-axis rotated about the z-axis and then about the y-axis. Varying the rotations provides two functions:
(a) Construction of any line, any arc, or any curve in three space; and
(b) Orientation of the constructed line or arc in any direction in three space.
In constructing display formats using the invention, a processor is required to specify only the size, orientation, and location of objects. The processor can then be used to manage the display format and is not required to process the point-by-point drawing of the display format.
It is one object of the invention to balance hardware and software tasks to efficiently construct display formats that require high throughput and image stabilization.
One advantage of the invention is that it allows objects to be created off-line as three dimensional icons and prestored symbols.
It is yet another advantage of the invention that display format objects created using the invention have the inherent ability to be rotated, translated, and scaled.
Yet another advantage of the invention is that the method of the invention is well suited for implementation in a pipeline architecture resulting in increased system throughput as compared to prior art systems.
Yet another advantage and feature of the invention is that the display processor is not loaded by the computationally intensive display generation task as in prior art systems.
Yet another advantage of the invention is that display figures may be occluded with display processors implementing a Z-buffer device.
Yet another advantage of the invention is that display figures may be displayed with depth cuing for display processors that implement a depth cuing function using the Z-values resulting from the invention.
Other objects, features and advantages of the invention will become apparent to those skilled in the art through the claims, description and drawings herein wherein like reference numerals refer to like elements.